Antenna



v. H. RuMsEY oct. 1o,y 195o -AN'TENNL 'Filed sept. 14. 194s ssheets-sheet 1- :Ezi-

5 Sheets-Sheet 5 VICTOR H RuMsEY v. H. RuMsEY ANTENNA Oct. 10, `1950Fund sept 14 1945 Oct. l0, V1950 v. H. RuMsEY 2,524,993

ANTENNA Filed sept. 14, 1945 5 sheets-.sheet 4 l VICTOR H RUMSEY wwwOct. 10, 1950 v. H. RuMsEY 2,524,993

ANTENNA Filed sept. 14, 1945 5 sheets-sheet 5 VICTOR' H. RUMSEY PatentedOct. 10, .1950

UNITED STATES PATENT OFFICE ANTENNA Victor H. Rumsey, Washington, D. C.,assigner to -the Minister of Supply in His Majestys Government vof theUnited Kingdom of Great Britain and Northern Ireland, London, EnglandApplication September 14, 1945, Serial No. 616,411

5 Claims.

This invention relates to an antenna, and

' rmore particularly to an antenna having a broad bandimpedance-frequency response character- I An object of this invention isto produce an antenna which Willpresent an input impedance substantiallyconstant over a wide band of frequencies.

" Another object o f this invention is to produce fanV antenna arraywhich will have substantially omni-directional4 radiationrproperties ina given plan'ef v A further object of thisinvention is to devise jjimproved means for translating energy between fjconcentric linev feedingan antenna Iand the antenna radiators.

#A rstill further object of this invention is to'provide an antennaarray feeder system having the property that the input impedance of theantenna radiator elements will match that fof a concentric transmissionline feeding the antenna, over a Wide band of operating frequencies. Inaccordance with these objects, and with Fig. 2 illustrates asectionalized plan view of 1 the antenna array of Fig. 1 taken Ialongline v2 2 thereof;

Fig. 3 is ar view, partially schematic, ofthe transforming vmeanswhereby energy is translated from an unbalanced, concentric trans-"misson'line to f a balanced transmission line feeding the radiatorelements;

" Fig. 4 illustrates one of the radiating elements f Fig. 1 used alone;

Fig. 5 is a perspective view of the antenna and housing of Fig. 4;

Fig. 6 illustrates the horizontal radiation pattern produced by theantenna array of Figs.

l Fig. 7 is a schematic diagram illustrating the operation of thematching transformer shown in Fig. 3; and

Fig.. 8 illustrates, somewhat schematically, the

antennaarray ofFig. 1, giving preferred dimensions for certain oftheparts.

Referring now to the drawings, Fig. 1 illus- ..3 trates an antenna arrayembodying this invenf tin and Vcornprising'a reflector having con-.'ducting vreflector plates I0 and II.

supports a pair ofdouble cone radiators I2 and I3, by means of rOds I4and I5 attached to the respective mid points of the radiators. Supportedby reflecting plate II are radiators 20 and 2l, corresponding,respectively, to radiators I2 and I3 supported by reflecting plate I0.

Each of the radiators is similar, for example, to radiator l2, whichconsists of a pair of cones I6 and II placed base to base, with theircommon axis along a vertical line. Radiators I2 and I3 are eachapproximately one-half wave length long at the mid point of their broadoperating band of frequencies, thus constituting together a full wavedipole, each radiator of which has the special double-conedconfiguration described above.

Energy is translated between concentric feeder line 22 and the radiatorsI2, I3, 20 and 2| by ymeans of a special matching transformer 23 shownmore particularly in- Fig. 3. Concentric line 22, consisting of innerconductor 24 and outer conductor 25, is separated from, and supportedby, reflecting plates I0 and II by means of spacers 26 and 21, and isterminated in the matching transformer 23 which will now be described.

Referring to Fig. 3, matching transformer 23 will be seen to consist ofinner conductor 24 and outer conductor 25, forming an extension ofconcentric line 22. In the end of outer conductor 25, are cut a pair ofdiametrically opposed slots 3E! and 3|, bifurcating outer conductor 25into two branches, 32 and 33. At the end of branch 33 a conductingsegment 34 is attached, forming an electrical connection between the endof branch 33 and inner conductor 24. From branch 32 of bifurcate outerconductor 25 eX- tends one side of a balanced transmission lineconsisting of electrically paralleled conductors 35 and 36 connected topredetermined points on radiators I2 and 20, respectively. Similarly,the other side of the balanced transmission line, consisting ofelectrically paralleled conductors 40 and 4I, is connected at one endtobranch 33 of bifurcate conductor 25 and at the other end to radiatorsI3 and 2|. In practice, slots 3l! and 3l are made equal approximately toa quarter wave-length at the mid-point of the frequency band to betranslated. Conductors 35, 36, 4D, and 4I are each Ymade equalapproximately to Va quarter wave length, for a purpose whichV will bedescribed hereinbelow.

In operation, when the antenna of Fig. 1 is used, for example, as atransmitting antenna, energy will be transmitted upwardalong concenwaveline shortcircuited at end E9.

tric, unbalanced transmission line 22. In transformer 23, the unbalancedline 22 will be converted into a balanced line consisting of conductors35, 35 and 40, 4|. As shown, balanced line 35--46 extends through a hole43 in reflector I to a point near the extremities of radiators I2 andI3, A-whereconductor 35 is connected to radiator I2, and conductor f toradiator i3. These points of connection are chosen so that the input Ykimpedance to the radiating elements is slightly greater than that ofthe transmission line 35-40, as will be explained more fully below.

Radiator E2 being a half wave-length long, maximum current will exist inthe center thereof, while maximum voltage will exist at each end. 1twill thus be seen that the lower tip of radiator l2 is a point of highimpedance; by going upward along radiator I2, lower and 'lower impedanceis encountered until a minimum impedance appears at the center, wheresupport E4 joins radiator I2. -On the other hand, it willfbe seen thatincreasing vimpedance is encountered 'with outward movetween theconcentric feeder line 22 and radiators f l2 and I3.

It .will 'be clear that the saine considerations as have been `statedfor radiators l2 and I3 apply equally to radiators 20 and 2L The entireantenna array is shown surrounded by a non-conductive protectivecylinder M which, in the preferred.embodiment, is constructed ofPlexiglas. 1

if desired, any ofthe radiating eieinents l2, 53,

2li or 2l maybe used as an individual. antenna in a manner illustratedin Fig. 4. In Fig. l the double-cone antenna t is end fed at a highimpedance point, the transformation between the concentric feed line 5land end 52 of radiator 50 Abeing made through the use of a `coni-caltransi forming member comprising inner conductor 53 fand outer conductor'556. An insulating disc 55 serves to support the antenna lin Vastreamlined housing 5S, which maybe made Yof Plexiglas or polystyrene.in the streamlined housing 56 is shown in Fig. 5.

Reference to Fig. -6 will demonstrate the substantially omnidirectionalradiation pattern ob- -tainedfrom the antenna array of Fig. 1. To obtainthis pattern dipoles iii-I3 and iid- 2l were placed as close together asfeasible. The optimum width of reliectors it and il was found to beapproximately one-third wave length (M3).

Theoperation of matching transformer 23 will 'best be understood byreference to Fig. 7, wherein the electrical elements comprising thetransformer have been shown schematically. Conductors 'and iiiconstitutea balanced transmission line translating energy between radiators i2-l3Hand'the ends of branches 32 and 33 of bifurcate outer conductor 25.Along vor'anches32 and 33, transmission line 3'5--43 `looks into aquarter- Along inner conductor v2li and branch 32, Yline SE-'ll looksinto a quarter-wave line 32-24, to the end of A perspectiveview ofantenna 5i) which is connected the unbalanced concentric line Z4-25. Itwill thus be seen that by use of the slots 3U and 3l, a quarter-wavetransforming section has been created, which serves to transformbalanced line Sli-40 into unbalanced line 24-25.

If the matching transformer were not used, and if one of the balancedcondu-ctors were simply connected to inner conductor 24 while the otherwere connected to outer conductor 25, energy would flow out of the endof the concentric line 22 and down around the outside of outer conductor25, so that any contact made to the outside of conductor would disturbthe energy iow and create serious mismatch in the system. For thisreason it is necessary to use a matching means as `described inconnection with transformer 23.v

Fig. 8 illustrates schematically the antenna array of Fig. 1 giving themagnitude of certain critical dimensions in terms of the wave length atthe mid-point of the frequency band to be radiated or received. While ithas been found that certain-of these dimensions must be held within areasonably close tolerance of approximately 25%, it will be apparentfrom the speciiication and appended claims that certain features of thisinvention are entirely free from critical dimensions. For example, theindividual radiators, when used alone as illustrated in Fig. 4, shouldbe equal to an odd number of half-wave lengths -and should bealternately slender and thick at each qua-rter wave point asillustrated. On the other hand, thespacing between radiators andreectors should-be as close as possible with- -out Vintroducingundesirable cancellation of signal strength due to out-of-phasereiection at'the reector.y The dimension `given constitutes simply onereasonable value which gives satisfactory operation.

Broad band operation of the antenna. array of Fig. l is dependenton anumber of factors, one of which-is the particular conguration of theindividual radiators I2, I3, 2t and 2l. AEach of these radiators is sofashioned that a small coni ducting surface is presented in regions ofhigh voltage, resultingin small capacitance; whereas a large surf-acefor current flow is presented in regions of high current, resulting inlow inductance. Inasmuch as current iiow will be largely confined tothe'surface of the radiator, it is to be understood that the importantdimension in the double cone radiator is-in addition to the halfwavelength-the periphery of the cross section taken normal to thelongitudinal axis at any given point.

Even with lthe special double-coned radiator configuration, the inputimpedance to the radiator will vary over the frequency band, going frominductive to capacitive reactance as the frequency increases. In orderto compensate for this change in impedance, thereby further to enhancethe broad band characteristic lof the array, certain compensatingfeatures are introduced. The lengt-h of a Afeeder line from the end oftransformer 23 to the connecting point on a radiator-e. fg., the lengthof line -is made Yequal approximately to a quarter wave length at themid point of the frequency band. The impedance vof transmission line35-40 at its outer end is made slightly greater than the input impedanceto the radiators I2. and i3 at the points of juncture. The decreasingimpedance of line 3,5/- as one moves toward the reflector serves -toenhance this compensation. Final compensa-tion is provided by thefshuntreactance `of the matching transformer. 23,1. e., transmission line32-33 (seeY Fig. 7)'. The final compensation thus invtroducedis greatestwhen the slots 30 and 3l are narrow, lwhile a lesser degree ofcompensation is introduced by widening the slots.

The features described above, comprising transformer 23, feeder lines35-40 and 313-41, and

double-coned radiators l2, I3, 20 and 2|, produce a broad band frequencyresponse for the array, by providing proper impedance transformation atthe mid-point of the frequency band, as well as f'optimum compensationfor radiator impedance variation over the Width of the band to betranslated.

vThe particular omnidirectional pattern illustrated'in Fig 6 is obtainedby making the refiector ffar as is necessitated by prior art andv thespirit .f of the appended claims.

vWhat is claimed is:

1. An antenna and feeder system comprising a reector, a pair of`Velongated radiating elements Y each a half wave length long at themid-frequency point of operation disposed along a common axis spacedless than a quarter-wave length at the vmid-frequency point of operationfrom said relflector, and a pair of diverging conductors extending thrua hole in said reflector and connectedrespectively to said pair ofelements at points thereon which display an impedance slightly less thanthe impedance of said diverging conductors at the points of theirconnection to said radiating elements, and a matching transformer havingone side connected to said conductors, and the other side connected to aconcentric transmission line.

2. An antenna array and feed system comprising a dipole including a pairof radiating elements each one-half wavelength long at the mid-frequencypoint of operation and each characterized by a `cross sectionalperiphery varying from a small fractional part of a quarter Wavelengthat each end of the radiator to substantially a quarter wave length atthe mid-frequency point of operation near the center thereof, and a pairof divergent` conductors forming a balanced feeder line for saidradiators connected to said radiators,

v respectively, at points thereon which disp-lay an impedance slightlyless'than the impedance of said divergent conductors at the point ofconnection thereof to said radiators, and a matching transformer havingone side connected to' said divergent conductors and the other sideconnected to a concentric transmission'line.

3. A substantially omnidirectional antenna arfray `comprising a pair of.juxtaposed vertical, di-

poles one wavelength long at the mid-frequency pointA of operation andspaced apart substantially one-half wave length at said frequency, and areflectordisposed between said dipoles with the 6 plane thereof normalto the common vertical plane passing through said dipoles, saidreflector having a horizontal width equal substantially to a third of awave length of said frequency.

4. An omnidirectional antenna array and feeder system comprising a pair`of parallel, closely adjacent relecting plates, a concentrictransmission line positioned between said plates, a matching transformerhaving one side connected to an end of said concentric line, two pairsof divergent conductors forming a pair of balanced transmission lineseach connected to said matching transformer and extending through arespective refleeting plate, and a pair of dipoles each one fullwavelength long at the said frequency point of operation respectivelyconnected to said balanced lines at points on said dipoles matching theimpedan-ce of said balanced lines.

5. An antenna array and feed system comprising a full Wave dipole, eachhalf radiator of which is one-half wavelength long at the mid-frequencypoint of operation and each characterized by a cross sectional peripheryvarying from a small fractional part of a quarter wave length at saidfrequency at each end to substantially a quarter wave' length at saidfrequency near the center thereof, and a pair of divergent conductorsforming a balanced feeder line for said radiators connected at its wideend to said radiators at points thereon intermediate the adjacent endsof said radiators and the respective centers thereof and a matchingtransformer havingv Aone side connected to the small end of saiddivergent conductors and the other side to a concentric transmissionline.

VICTOR I-I. RUMSEY,

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,884,006 Lindenblad Oct. 25,1932 1,939,345 Gerth et al Dec. 12, 1933 2,104,610 Dome Jan. 4, 19382,115,826 Norton et al May 3, 1938 2,163,770 Von Radinger June 27, 19392,183,784 Carter Dec. 19, 1939 2,235,015 Eggers Mar. 18, 1941 2,237,778Carter Apr. 8, 1941 2,249,963 Lindenblad July 22, 1941 2,267,889 AubertDec. 30, 1941 2,275,646 Peterson Mar. 10, 1942 2,417,895 Wheeler Mar.25, 1947 2,430,353 Masters Nov. 4, 1947 2,433,698 Hurst Dec. 30, 19472,455,403 Brown Dec. 7, 1948 FOREIGN PATENTS Number Country Date 520,849Great Britain May 6, 1940 877,658 France Dec, 14, 1942

